Hematopoiesis is sustained by a rare population of hematopoietic stem cells (HSCs) capable of self-renewal and differentiation into multiple hematopoietic lineages. These HSCs include a long-term repopulating (LTR) subset that is capable of complete hematopoietic regeneration. The ability to maintain or expand the LTR population of hematopoietic stem cells in vitro and in vivo without inducing their differentiation is crucial for clinical applications, such as gene therapy and the expansion of stem cells and progenitor cells for transplantation.
During the last decade, considerable progress has been made towards the isolation and characterization of primitive hematopoietic cell populations in mice and humans. From this body of work, several hematopoietic stem cell identifiers, i.e., cell-surface markers found on hematopoietic stem cells, have been delineated which have proven to be highly useful for the identification and isolation of hematopoietic stem cells. Novel identifiers of hematopoietic, long-term repopulating cells remain of interest, as the identification of novel stem cell markers may provide access to previously unknown subsets of rare hematopoietic stem cells.
Despite the number of cell surface markers that have been delineated to date, the identification and uses of rare populations of hematopoietic stem cells capable of tissue repair and regeneration remains uncharted territory. Rare stem cell populations that are related to lethal radiation survival in animal models might prove to be useful in the therapeutic areas of repair and regeneration of hematopoiesis and also other tissues types within the body, such as brain tissue, lung tissue, kidney tissue, pancreatic tissue, liver tissue, or cardiac tissue and the like. Thus, the identification of novel stem cell markers that can delineate a rare population of stem cells useful in hematopoietic tissue repair and regeneration, as well as general tissue repair and regeneration, are still needed in the areas of regenerative medicine.